Molecular and Electronic Structures of the Members of the Electron Transfer Series [Mn(bpy)3]n (n = 2+, 1+, 0, 1−) and [Mn(tpy)2]m (m = 4+, 3+, 2+, 1+, 0). An Experimental and Density Functional Theory Study

The members of the electron transfer series [Mn­(bpy)3]n (n = 2+, 1+, 0, 1−) and [Mn­(tpy)2]m (m = 2+, 1+, 0) have been investigated using a combination of magnetochemistry, electrochemistry, and UV–vis–NIR spectroscopy; and X-ray crystal structures of [MnII(Mebpy•)2(Mebpy0)]0, [Li­(THF)4]­[MnII(bpy•)3], and [MnII(tpy•)2]0 have been obtained (bpy = 2,2′-bipyridine; Mebpy = 4,4′-dimethyl-2,2′-bipyridine; tpy = 2,2′:6,2″-terpyridine; THF = tetrahydrofuran). It is the first time that the latter complex has been isolated and characterized. Through these studies, the electronic structures of each member of both series of complexes have been elucidated, and their molecular and electronic structures further corroborated by broken symmetry (BS) density functional theoretical (DFT) calculations. It is shown that all one-electron reductions that comprise the aforementioned redox series are ligand-based. Hence, all species contain a central high-spin MnII ion (SMn = 5/2). In contrast, the analogous series of TcII and ReII complexes possess low-spin electron configurations.

本研究结合磁化学、电化学与紫外-可见-近红外（UV–vis–NIR）光谱技术，对电子转移系列配合物[Mn(bpy)₃]ⁿ（n = 2+, 1+, 0, 1−）与[Mn(tpy)₂]ᵐ（m = 2+, 1+, 0）的所有组分开展了系统表征；同时成功解析了[MnII(Mebpy•)₂(Mebpy⁰)]⁰、[Li(THF)₄][MnII(bpy•)₃]以及[MnII(tpy•)₂]⁰的X射线晶体结构，其中bpy = 2,2′-联吡啶，Mebpy = 4,4′-二甲基-2,2′-联吡啶，tpy = 2,2′:6,2″-三联吡啶，THF = 四氢呋喃。其中后一种配合物的分离与表征尚属全球首次。通过上述研究，我们阐明了这两个系列配合物各组分的电子结构，并通过破对称（broken symmetry, BS）密度泛函理论（density functional theoretical, DFT）计算进一步验证了其分子与电子结构。研究结果显示，构成上述氧化还原系列的所有单电子还原过程均为配体中心反应，因此所有物种均含有一个中心高自旋MnII离子（SMn = 5/2）。与之形成鲜明对比的是，类似的锝II（TcII）与铼II（ReII）配合物系列则呈现低自旋电子构型。